Some of them haven't learned the nuances of how I speak and think yet.
When I say, "I don't think this will work," about something I'm doing, with the inflection that means, "I'm really serious, I mean this, and I say this after hours mulling it over", the response "Just give the guy a chance!" said with the "I know you're hung up on the other guy, but many fish, big sea" inflection, says to me that the person who's advising me to give the guy a chance doubts the validity of my certainty that it's not going to work.
Which says, to the undermind, that they don't trust my perceptions.
And the undermind says, "Well, you trust THEIR perceptions, don't you? Maybe they've got a point."
So, against your better judgement, you extend the "chance"... and you were right. It wasn't going to work. You knew it. You knew it already.
...You just doubted yourself.